CopyChecker._checkArchiveConflicts forbids copies with builds in progress where the building architecture does not exist in the target

I modified sru-release in lp:ubuntu-archive-tools to use Archive.copyPackage, and used it to copy compiz-plugins-main 1:0.9.6-0ubuntu4.2 from Ubuntu oneiric-proposed to Ubuntu precise and then to Ubuntu oneiric-updates, in two API calls. The first succeeded but the second failed. Falling back to Archive.syncSource I could see the reason:

  compiz-plugins-main 1:0.9.6-0ubuntu4.2 in precise (same version already building in the destination archive for Precise)

The build in question was https://launchpad.net/ubuntu/+source/compiz-plugins-main/1:0.9.6-0ubuntu4.2/+build/3073902, which is an armhf build. This cannot possibly conflict with a copy to oneiric-updates because the armhf architecture was not present in oneiric. CopyChecker._checkArchiveConflicts should permit this situation rather than forbidding it.

I eventually got Archive.syncSource to work after waiting for this build to publish. Archive.copyPackage never worked for me here; since it doesn't leave feedback anywhere I can find (Julian suggested +localpackagediffs, but https://launchpad.net/ubuntu/precise/+localpackagediffs?field.name_filter=compiz-plugins-main&field.package_type=all&field.package_type-empty-marker=1 didn't show anything, presumably because this is a copy from oneiric-proposed not from wheezy - oh, but now I realise I should perhaps have checked https://launchpad.net/ubuntu/oneiric/+localpackagediffs?field.name_filter=compiz-plugins-main&field.package_type=all&field.package_type-empty-marker=1 instead, but it's too late now), I couldn't find out whether I was just running into some later error, or whether I simply didn't wait quite long enough.